1. Field of the Invention
The present invention relates to a snowmobile, in particular to a snowmobile in which a knuckle is connected to a vehicle body frame via an arm.
2. Description of the Related Art
In a snowmobile, the structure of a portion of the suspension is known to include a knuckle to which a ski is connected, and the knuckle is in turn connected to an arm which further connects to a vehicle body frame. The knuckle is interposed between the arm to which the suspension is connected and the ski, and transfers the movement of the ski to the arm. In FIG. 39 of U.S. Pat. No. 6,655,487, the arms 454, 456 are connected to the front leg 458 via the pin 466 or the like, and the input from the handlebar 474 is transferred to the steering shaft 470 and the ski 464 via the mechanical linkage 476. Such structure is complex, heavy and costly. In view of such problems, FIG. 42 of U.S. Pat. No. 6,655,487 discloses a structure in which the arm is connected to the knuckle using a ball joint and the like, the extension portion 516 outwardly projects from the frame which defines the knuckle, and the ball joint is supported by the extension portion 516. This structure can have a lower cost and lighter weight as compared with the structure in FIG. 39 of U.S. Pat. No. 6,655,487.
However, in the aforementioned knuckle, when the ball joint is supported by the extension portion 516 projecting outwardly from the frame which defines the knuckle, stress is easily concentrated on a portion of the extension portion 516. Therefore, in order to maintain a required strength, the knuckle and the extension portion 516 have to be made of a sufficiently thick member, which causes an increase in cost and weight. Therefore, a low cost and light weight member serving as a connection member of the arm and the knuckle is desired.
Snowmobiles, in particular, are for moving on the snow, and are required to negotiate not only relatively flat snow surfaces like a paved road but often also extremely rough snow surfaces. When traveling on an extremely rough snow surface, the two skis provided on the right and left sides of the vehicle body of the snowmobile may move significantly up and down. In addition, the height of the two skis may change abruptly due to a sudden change in the elevation of the snow surface. Under this situation, as compared with traveling on the flat snow surface, extremely large forces act on the skis. Thus, the snowmobile requires a high strength connection member between the arm and the knuckle.